1. Field of the Invention
The present invention relates to an optical module and an optical amplification module.
2. Description of the Related Art
Processing technology using a laser beam is receiving attention, and the demand for an optical amplification module that can generate a high power laser beam is increasing in respective fields, including the medical field. For an optical amplification module, a double clad type where an optical fiber in which a rare earth element that can be excited by an pump light is added to the core area is used as an optical fiber for application, is known, as stated in Koji Sugioka and Akira Yabe, “Laser Micro Nano Processing”, First Edition, Japan, CMC Publishing, November 2004, pp. 67-68 (hereafter called the Non-patent Document), for example. The optical amplification module stated in the Non-patent Document is used as a fiber laser light source, and supplies the pump light to the optical amplification fiber using an optical module comprised of and LD with a fiber and optical coupling means.
A to-be-amplified light and an pump light are supplied to an optical amplification fiber of an optical amplification module normally using an optical module, as shown in FIG. 7 and FIG. 14.
An optical module 140 of an optical amplification module 130, shown in FIG. 7, is comprised of an pump light source 40 and optical coupling means 50 which are optically connected via an optical fiber 141, and the pump light from the pump light source 40 is input to the optical coupling means 50 through the optical fiber 141. Also in the optical amplification module 130, a light source 10 is optically connected to an optical fiber 51 of the optical coupling means 50, and the optical coupling means 50 multiplexes the to-be-amplified light, which is output from the light source 10, and an pump light, which is output from the pump light source 40, and inputs it to an optical amplification fiber 20. As a result, the to-be-amplified light is optically amplified in the optical amplification fiber 20, and is output as high power light.
An optical module 160 of an optical amplification module 150, shown in FIG. 14, is comprised of an pump light source 40 and optical coupling means 170 for multiplexing an pump light and a to-be-amplified light and for inputting the multiplexed light to an optical amplification fiber. The optical coupling means 170 is further comprised of an optical fiber 51 as an input port of the to-be-amplified light, an optical fiber 171 as an input port of the pump light, an optical coupling section 53 as a multiplexing medium of the to-be-amplified light and the pump light, and an optical fiber 54 as an output port, and a light source 10 is connected to the optical fiber 51 and an optical amplification fiber 20 is connected to the optical fiber 54. By this configuration, the to-be-amplified light and the pump light, which are output from the light source 10 and the pump light source 40, are input to the optical amplification fiber 20 via the optical coupling means 170. And the to-be-amplified light is optically amplified in the optical amplification fiber 20, and is output as high power light.
In order to output an even higher power light from the optical amplification fiber 20 in the above mentioned optical amplification module 130 and 150, multi-mode fibers for propagating the pump light in multi-mode could be used as the optical fiber 141 and the optical fiber 171.
However if the optical amplification fiber 20 in the optical amplification modules 130 and 150 is connected to another optical fiber, shown in FIG. 7 and FIG. 14, a connection loss is generated in the connected portion, and the to-be-amplified light for the amount of this loss may propagate in the optical amplification fiber 20 in a direction opposite from the propagation direction of the pump light. In this case, if the optical fiber 141 or 171 is a multi-mode fiber, the multi-mode fiber has the nature to easily confine light, other than the pump light, in the fiber because the core diameter and NA are large, so high power to-be-amplified light, which propagates in a direction opposite from the pump light, may propagate to the pump light source 40. In this case, the pump light source 40 may be damaged and operation thereof may become unstable, then pump light may not be able to be stably supplied to the optical amplification fiber, and as a result, high power light may not be generated.
With the foregoing in view, it is an object of the present invention to provide an optical module and an optical amplification module which can stably supply pump light to an optical amplification fiber.